Quirc is a library for extracting and decoding QR codes from images. It has
several features which make it a good choice for this purpose:

  * It is fast enough to be used with realtime video: extracting and decoding
    from VGA frame takes about 50 ms on a modern x86 core.

  * It has a robust and tolerant recognition algorithm. It can correctly
    recognise and decode QR codes which are rotated and/or oblique to the
    camera. It can also distinguish and decode multiple codes within the same
    image.

  * It is easy to use, with a simple API described in a single commented header
    file (see below for an overview).

  * It is small and easily embeddable, with no dependencies other than standard
    C functions.

  * It has a very small memory footprint: one byte per image pixel, plus a few
    kB per decoder object.

  * It uses no global mutable state, and is safe to use in a multithreaded
    application.

  * BSD-licensed, with almost no restrictions regarding use and/or modification.
